1. Field of the Invention
This invention relates to a drilling fluid degasser used in the oil and gas industry for the removal of associated gases that are released from the formation into the drilling fluid so that the drilling fluid may be recycled and reused in the drilling operations. More specifically, the present invention concerns a drilling fluid degasser using a vacuum chamber to which a vacuum pump is connected to produce a differential pressure between the vacuum chamber and the atmosphere.
The drilling of oil and gas wells utilizes a drill bit suspended a drill string that extends from the drilling rig to the bottom of the well bore being drilled. The drill string is an assembly of hollow pipes threaded together to form a continuous fluid conduit. During drilling operations, drilling fluid or xe2x80x9cmudxe2x80x9d as it is frequently referred to in the oil and gas industry is pumped down the drill string and out through ports in the drill bit. The drilling fluid is forced back up the annulus between the outside of the drill string and the well bore to the surface where it is processed for reuse. This overall system of mud processing is described in detail in U.S. Pat. No. 5,853,583 to Dilipkumar Shah, inventor of the present invention and assigned to the same assignee as this application.
An important aspect of the drilling fluid processing before reusing is the removal of entrained gases, such as methane and any other gases released from the formation including hydrogen sulfide, from the drilling fluid. The aforementioned pumping of the drilling fluid under pressure down the drill string is accomplished by duplex or triplex mud pumps having reciprocating pistons in cylinders for pressurizing the drilling fluid. If the entrained gas is air the efficiency of the pump is reduced. In the case of methane gas, if it is not removed by the degasser and disposed of properly, there is a danger of fire or explosion from the entrained methane gas.
Typical vacuum drilling fluid degassers use the differential pressure between the interior of the vacuum chamber and the outside atmosphere to cause gases to bubble up out of the drilling fluid where it drawn out of the degasser. The efficiency of this process is improved by allowing the drilling fluid to flow over leaves or conically shaped plates in the degasser in a thin film. This dispersion of the drilling fluid in a thin film over the leaves allows the bubbles entrained in the drilling fluid to more easily break loose from the drilling fluid, then burst and release their gas to the interior of the vacuum chamber where it drawn away by the vacuum pump. The removed gas is then routed to a safe distance from the rig and vented to the atmosphere or burned in a gas flare.
It is therefore important that the degasser function reliably and efficiently to remove the aforementioned entrained gases. The present invention accomplishes these goals in two respects. First a unique weir or gate is added to more evenly spread the drilling fluid over the leaves of the degasser to increase the efficiency of the degasser. Second a plurality of gas vent pipes are added to the degasser that ensure that once the gases are removed from the drilling fluid, the gases are removed from the degasser without contacting the drilling fluid to ensure the gases are not mixed into the drilling fluid again.
2. Description of Related Art
U.S. Pat. No. 4,668,251 to Harry L. Burgess shows a modified drilling mud degasser used to simultaneously degas drilling mud and supercharge a mud pump to which the degassed mud is delivered.
U.S. Pat. No. 4,872,530 to Harry L. Burgess discloses a self-lubricating centrifugal mud degasser.
U.S. Pat. No. 4,957,187 to Harry L. Burgess shows a gear-driven degasser for removing gases.
The present invention comprises a vacuum chamber having a cylindrical vessel with a hemispherical head or cap welded to each end to form the enclosed chamber. A vertically oriented drilling fluid inlet pipe is centrally located within the vacuum chamber. A plurality of fluid dispersion leaves are spaced vertically along the drilling fluid inlet pipe. The drilling fluid inlet pipe has a plurality of drilling fluid distribution outlets disposed circumferentially around the drilling fluid inlet pipe adjacent each of the fluid dispersion leaves at an elevation above the fluid dispersion leaves. The fluid dispersion leaves have a annular inner section sealingly secured to the drilling fluid inlet pipe and a conical outer section sealed to the annular inner section. The conical outer section extends radially outwardly to close proximity with the outer wall of the vacuum chamber. A fluid dispersion weir is disposed on each fluid dispersion leaf, encircling the plurality of circumferentially spaced drilling fluid distribution outlets. The fluid dispersion weir has a saw toothed upper edge to allow drilling fluid to pool behind the weir before spilling over the saw toothed edge in an even pattern. Additionally, each fluid dispersion leaf has a plurality of gas vents or stand pipes thereon to allow venting of gases extracted from the drilling fluid to pass upwardly through successive fluid dispersion leaves without contacting the drilling fluid.
A principal object of the present invention is to provide a drilling fluid degasser that uses a weir on the leaves to enhance even distribution of the drilling fluid over the leaves and thereby increase efficiency of the degasser.
A final object of the present invention is to provide a drilling fluid degasser that uses a unique system of gas vent pipes located on the leaves of the degasser to ensure gas removed from the drilling fluid is not remixed with the drilling fluid as it is evacuated from the degasser.
These with other objects and advantages of the present invention are pointed out with specificness in the claims annexed hereto and form a part of this disclosure. A full and complete understanding of the invention may be had by reference to the accompanying drawings and description of the preferred embodiments.